Abstract

Objective: To assess the mechanisms through which an enlarged aortic root may facilitate right to left shunting through a patent foramen
ovale.

Patients: 19 patients with the platypnoea-orthodeoxia syndrome (POS) were compared with 30 control patients without platypnoea.

Interventions: Multiplane transoesophageal echocardiography.

Main outcome measures: The aortic root diameter, atrial septal dimension behind the aortic root, and amplitude of the phasic oscillation of the
septum were measured. Four groups of patients were compared: 12 platypnoeic patients with a dilated aortic root (POS-D), 7
platypnoeic patients with a normal aortic root (POS-N), 15 control patients with a dilated aortic root (CONT-D), and 15 control
patients with a normal aortic root (CONT-N).

Conclusion: Patients with an enlarged aorta have an apparently smaller dimension and increased mobility of the atrial septum. These findings
appear to result from compression by the aortic root and decreased septal tautness. Consequently, a “spinnaker effect” with
the inferior vena caval flow may take place, opening the foramen ovale and leading to sustained right to left shunting.